DENVER — Colorado voters split on taxes Tuesday, giving a resounding yes to a tax on retail marijuana and an equally emphatic no to an income tax increase aimed at funding K-12 education.

Proposition AA, which would place a 15 percent excise tax and sales taxes of up to 15 percent on retail marijuana, was leading by a margin of 65 percent to 35 percent with 84 percent of the vote counted, according to early election returns.

“Colorado is demonstrating to the rest of the nation that it is possible to end marijuana prohibition and successfully regulate marijuana like alcohol,” said Mason Tvert, spokesman for the Marijuana Policy Project, which supported Proposition AA and was the largest financial backer of the Amendment 64 campaign in 2012. “It is only a matter of time before voters and lawmakers in other states recognize the benefits and adopt similar policies.”

Meanwhile, Amendment 66, the proposed $950 million income tax increase for education backed by Gov. John Hickenlooper and fellow Democrats in the General Assembly, was going down to defeat by 66 percent to 34 percent.

The loss of Amendment 66 came as a double-whammy in Colorado for New York City Mayor Michael R. Bloomberg. He sunk $1 million into the $10 million tax hike effort, just two months after bankrolling losing campaigns to save two Democratic state senators from recall drives.

The two Democrats, state Sens. Angela Giron and John Morse, lost the Sept. 10 recall votes after being targeted for their support in favor of gun control bills backed by Mr. Bloomberg.

“When can we expect Bloomberg’s concession that he’s lost Colorado?” state Rep. Frank McNulty, a Republican, said in a tweet.

Marijuana sales tax proposals in several Colorado municipalities, including Boulder, Denver and Littleton, also were leading in the polls late Tuesday. The local sales taxes would come in addition to the state sales tax.

Opponents of the state marijuana taxes argued that some jurisdictions could wind up with a sales tax of as much as 52 percent, which would encourage the development of a black market.

Even so, analysts said, voters are much more likely to approve “sin taxes” on items such as cigarettes and alcohol, and now marijuana, than income taxes.

“Is Colorado more comfortable with sin taxes or income taxes?” Denver pollster Floyd Ciruli said in his pre-election analysis. “Bet on sin.”

The state marijuana sales tax comes a year after Colorado voters approved recreational marijuana use for people 21 and older. During the campaign, organizers promised to support an excise and sales taxes on legalized marijuana in order to pay for enforcement and regulations.

Colorado and Washington became the first states to legalize adult recreational marijuana in 2012.

Under the Colorado legalization measure, Amendment 64, the first $40 million raised by the 25 percent excise tax goes toward school construction.

In New York, voters were considering whether to authorize the state legislature to expand gambling by approving up to seven casinos, an effort designed to bolster economic growth in upstate New York.

In Washington, a $22 million campaign was coming down to the wire over whether to require companies to label genetically modified foods. Fighting the initiative were the Grocery Manufacturers Association along with agriculture companies Monsanto, DuPont Pioneer and Bayer CropScience.

California voters narrowly rejected a similar GMO labeling proposal in 2012. If passed, the Washington measure would be the first of its kind in the nation.